This invention relates to length measuring apparatus, and particularly but not exclusively concerns a length measuring apparatus for measuring accurately the length dimensions of labels which are for application to cans, bottles, and similar containers.
As the description of the invention proceeds, it will be understood however, that the actual article which is having its length dimensions measured is immaterial as long as that article has the geometric characteristics to fit the apparatus. An article which has such characteristics can have its length dimensions accurately measured, and length dimensions can and do include height and width.
As the apparatus was invented specifically to enable the accurate measurement of lables for cans, bottles or the like, reference will be made hereinafter only to the length dimensions of labels, but the views expressed above require the specification, unless the context specifically indicates or implies otherwise, to be construed accordingly.
The application of labels to metal cans, such as beer cans, takes place at high speed, i.e. of the order of 600 to 900 labels per minute, and as labels are consumed at this speed from magazines, it is important that the labels be manufactured dimensionally to a high degree of accuracy. If they are not, then there can be problems with the extraction of the labels from the magazine. This is due to the fact that the labels are stacked so that the individual labels are in substantially vertical disposition, and if a batch of labels is taller than an adjacent batch, then they cause a distinct step in the top surface created by the stacked labels, and this step causes considerable difficulties in the high speed feeding of labels from the magazine.
Customers therefore demand of label manufacturers that as regards labels for the above application, they must be manufactured to a high degree of accuracy. Label manufacturers must therefore quality control the manufacture of labels and continuously and conscientously check label length dimensions.